/**
 *    Copyright 2009-2019 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.scripting.xmltags;

import org.apache.ibatis.builder.xml.XMLMapperEntityResolver;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.parsing.PropertyParser;
import org.apache.ibatis.parsing.XNode;
import org.apache.ibatis.parsing.XPathParser;
import org.apache.ibatis.scripting.LanguageDriver;
import org.apache.ibatis.scripting.defaults.DefaultParameterHandler;
import org.apache.ibatis.scripting.defaults.RawSqlSource;
import org.apache.ibatis.session.Configuration;

/**
 * @author Eduardo Macarron
 */
public class XMLLanguageDriver implements LanguageDriver {
    /**
     * 创建参数处理器
     *
     * @param mappedStatement The mapped statement that is being executed 正在的执行的声明语句
     * @param parameterObject The input parameter object (can be null) 输入的参数对象
     * @param boundSql        The resulting SQL once the dynamic language has been executed. 生成的SQL
     */
    @Override
    public ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
        return new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
    }

    /**
     * 根据XML创建SQLSource
     *
     * @param configuration The MyBatis configuration Mybatis配置
     * @param script        XNode parsed from a XML file 从XMl文件解析的XNode
     * @param parameterType input parameter type got from a mapper method or specified in the parameterType xml attribute. Can be null.输入的参数类型
     */
    @Override
    public SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType) {
        // 动态元素解析器
        XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);
        // 构架SQL源
        return builder.parseScriptNode();
    }

    /**
     * 根据java注解创建SQLSource
     *
     * @param configuration The MyBatis configuration Mybatis配置
     * @param script        The content of the annotation 注解中的内容
     * @param parameterType 参数类型 input parameter type got from a mapper method or specified in the parameterType xml attribute. Can be null.
     */
    @Override
    public SqlSource createSqlSource(Configuration configuration, String script, Class<?> parameterType) {
        // issue #3
        // 处理包含动态SQL元素的配置
        if (script.startsWith("<script>")) {
            XPathParser parser = new XPathParser(script, false, configuration.getVariables(), new XMLMapperEntityResolver());
            return createSqlSource(configuration, parser.evalNode("/script"), parameterType);
        } else {
            // 常规SQL配置
            // issue #127
            script = PropertyParser.parse(script, configuration.getVariables());
            TextSqlNode textSqlNode = new TextSqlNode(script);
            if (textSqlNode.isDynamic()) {
                return new DynamicSqlSource(configuration, textSqlNode);
            } else {
                return new RawSqlSource(configuration, script, parameterType);
            }
        }
    }

}
